Junai

On his way to work, Shimizu, a systems engineer, faints at a train station because of his strenuous job. As everyone pretends not to see him, the only person to call out to him is his elementary school classmate, Suzuki. But when Shimizu wakes up again, he discovers that he has been imprisoned in a strange place, undressed and violated by the formerly kind Suzuki! "Looks like you get more excited when you're tortured." Day by day he drowns in sex inside his cell. His nipples, asshole and lips are toyed with until he can't take it anymore as his body is molded into something corrupt. His shame gradually starts to morph into pleasure... (Source: Libre, translated)